"Pompeii" corner WFBO project in Loei, Thailand

[terratree]

Spot on. Hopefully david s or someone can comment on how best to apply it.

[TxGR]

I asked them for the data sheet and they sent me a link (pic below). I had seen it before, but was primarily looking at the components. The way I read it now, this mortar is meant to be heated to cure, or at the very least, full strength is achieved after heating.



Here is the data on the brick. The brick I have is SK30, the first column.

[terratree]

I think your correct about keeping it moist for as long as possible. The slower it cures the better.

As for the brew, perhaps take a pic of the AM 30 contents/ratios, and post back for others to comment. I used the standard 3:1:1:1 and had no issues, except for average masonry skills of course

[TxGR]

I need to update the thread. I mortared in the inner arch columns and transition bricks from the soldiers to the columns. I went back over much of the brick I cleaned up.

The new work turned out pretty good. The lines are much thinner -- I think that is critical with this mortar. I also put wet rags over the work and I think that helped a lot. In the pics above, even after a week, they look partially wet. I think they were. The new stuff dried much faster -- that is reached a light gray color -- and there were no cracks in the new work. Where I did some rework, there were some cracks, but much smaller.

I am using a refractory mortar sold in Thailand by BTS called AM 30. It is pre-mixed and comes in sealed 5 gallon buckets. The instructions say remix to ensure it is homogenous, then apply to clean, dry bricks.

The bricks I used for the new work were slightly moist or dry. Some of them I had just cut with the wet saw, but they had been sitting for a little while. Others were dry. None of them were soaking, like the first bricks I did.

I had to drive my cat to the hospital in Bangkok. So I should be able to return to it by the end of the week.

[terratree]

I found a happy medium when wetting the bricks, a light spray or dip prior, seemed to work ok.

I didnt have flaky mortar like that though, what fire mortar mix are you using ? Perhaps one for Russell.

As i learned on this forum, you wont see the back end of any bricks - its all about the inside.

[TxGR]

So, I was gone for 7 days and only finished mortaring the soldiers in place. As per the pics I saw from others, I took the excess mortar and simply added a layer around the backsides of the bricks on half of the bricks. This did not work well.



This side I covered after it already started to dry. The bricks were soaked and removed 2-4 at a time. Then I put mortar on each side and placed the brick. Again, at 2-4 at a time, I filled gaps and packed more mortar in the gaps. On this side, I went back about 90 minutes later and slathered on additional mortar over the exterior. I also covered the ceramic fiber board and oven floor bricks (notice that didn't crack). I then placed a tarp over the project to prevent direct sunlight.



This is the opposite extreme from above; this is where I finished last Friday. I didn't have enough open mortar to go over this other than to kind of fill the gaps. Obviously, there is far less cracking.



This is the transition area where I ran out of excess mortar to go over the exterior.

Any thoughts?

Did it dry too quickly? I've seen people all my life spray down curing concrete to prevent it from curing too quickly. Should I have arranged to spray it down?

The instructions for this mortar clearly state the bricks should be dry. All the advice in the forum and on the FornoBravo plans say soak the bricks. Since the part that didn't crack was where I covered the oven floor and ceramic fiber board, does this mean for this mortar, dry is the right method?

Is it even fully cured yet? Looking at the second picture, I think the thick areas are still wet inside. If true, I think that supports the idea I need to stick around and spray water on the mortar to prevent it from drying too quickly.

Whatever did stick was enough -- the bricks are locked in solid -- they are not moving without a sledgehammer. I am not overly worried. If they were loose, or easily broke apart, I'd be very concerned. The joints on the inside are near zero gap. The exterior will all be covered.

Subject to suggestions, I am leaning toward trying dry brick on several bricks and spraying down soaked bricks on several others. The challenge is the next part will be visible because I have to do the columns for the arches. So, again subject to suggestions here, I will do the inner arch columns, then start on the second course of bricks, doing one side dry, one side pre-soaked. I'll only do a few of the second course bricks and will keep one side moist.

Any advice will be cheerfully appreciated.

[UtahBeehiver]

It is a 63-65% arch height to dome height is rule of thumb that provides the best effeciency of oven performance and venting. Are there exceptions, yes but if it only takes 15 seconds to lower, why not? As for the tapered inner arch, you start with full length bricks at the top dead center(TDC) of the arch (also the longest of the arch bricks) then work your way down each side of TDC using a combination of the IT for top slope and the previous brick cuts IE, looking from the inside of the dome outward, the left side of the TDC will be the pattern for the right side of the next brick left of TDC and visa versa for the right side of the TDC. Each brick is unique so you cannot cut the arch bricks all the same, they are not all the same in shape.

[TxGR]

There could be any number of reasons the mortar acted differently, especially my own inexperience. Since I have little masonry experience (plenty of watching, very little doing), I'm not really sure what mortar should act like. Accordingly, I might have found it easier as it was. Also, it's possible they changed the ratios/formula or one of us received old and one of us received new. This definitely goes on thinner than most mortar I've ever seen applied or in actual brick builds in Texas.

At the moment, I am in Chiang Mai. I was able to find a 9" (230mm) diamond (dry) blade with a 20mm arbor that will fit my table saw. That should allow me to make the more complex cuts for the archway. Worse case, I can get a chop saw for around THB3500 in Loei.

As UtahBeehiver suggested, I looked up the tapered arch on mrchipster thread (https://community.fornobravo.com/for...2-in-minnesota) and I think I know what I have to do for the arch starting at the corner. I'll probably have more questions when I get to that point.

I am sure I will learn a great deal and some of it will be by making mistakes.

Regarding the dome height, as I have it configured now, I think it is r55cm +11.5cm for a 66.5cm dome height. The inside arch height is 39cm (IIRC), making it 58.6%, so smaller than ideal. In reading through the forum threads, there were some (IIRC) with ratios even farther askew. I read some discussions about just how "golden" the ratio is in a practical sense. I don't know either way. If I put the IT at floor level, then it would be 70.9%. To achieve 63%, the IT should be 6.9cm above the floor (61.9cm dome height). In a sense, it's totally arbitrary. The "wood brick" is sitting on blocks to raise it as high as it is (actually, I think it is still a little low). In 15 seconds, I could lower it ~6cm. As I haven't started to place the second course yet, no rework is required. This doesn't even affect the cut on the top of the soldier bricks in a meaningful way.

How critical do you think the 63% ratio is and how precise does it need to be?

Thanks for the timely feedback. I can easily address this now. Later it will be impossible.

[UtahBeehiver]

Just be aware that by raising the IT platform, the dome height will be higher than the dome width at the base by the amount raised unless you make adjustments accordingly. This may affect the arch opening golden ratio of 63 to 65% of the dome height.

[Vinz]

Thanks for keeping us posted, looking very good and professional!

Also nice to see how the pre-work of the whole area was done.
Funny to read about different behaviour of the same wet-type mortar on the same bricks and even in a pretty similar geographic location (other season, though ;-) )
Wondering how the mortar will do after drying (if ever for real, prior to firing).
The wet mortar on the soldier bricks, in my case, i would be able to peel/chip it off the next day.

your prep-work and thinking it through is amazing. actually, i found the planning of this build a very enjoyable experience myself, as well as the knowledge I gathered about the materials involved

Good to see those good old heavy BST bricks being used again!
Regarding the cutting, I used an expensive diamond saw on one of these cheap Thai cutting tools (you got a picture of a guy using it to cut the rebar bars). Worked fine for the whole build, the blade is still good.

I noticed that in the dry-build you sometimes have the print on the bricks towards the inside of the oven. Then in the real build, it does not seem to be the case. Just wanted you to make sure there is no print pointing inwards, as this looks rather unnatural when you look inside (and there will be a lot of looking inside when cooking time comes).

Wetting the bricks for me was rather superficial, the BST bricks don't seem to soak up that much water. without the soaking, the bricks would draw the water out of the mortar way to fast, resulting in miniature cracks. At least for me at the time, now it looks like your mortar behaves totally different..
Regarding floor insulation, you got a bit less than me (i have a full BST brick as base which is thicker). I found the base insulation to be the weakest point in my build in hindsight. Also rebar bars in my opinion might drain the heat. I have an open table as a base however, which might ventilate more heat than your pretty much enclosed base. Hope that will help.

Looking forward to your next update!

[TxGR]

After checking all the alignment, time to elevate the base for the IT (indispensable tool) and cut bricks.


The top of each soldier was marked and cut for a 17* angle (6mm off the inside). The curve of the dome will start 11.5cm above the floor (half-way up the soldier bricks). If you've ever seen an observatory like the one at Mt. Palomar, there is a straight walled cylinder with a domed top. That is the intent of the full height soldier bricks. The curve of the dome will actually be measured half-way up the soldier bricks.

The brick last soldier next to the form in the upper right of the picture above needed to be trimmed lengthwise. So...that revealed a fundamental flaw in the type of wet saw I have (as predicted earlier on this forum by, I think, @UtahBeehiver). I eventually made the cut, but it looked very rough. The wet saw did fine for part of it, but even at an angle it won't slide over the brick or cut deep enough. I think I have a better solution for this now. For this one, I used a 4" grinder to finally finish the cut. Keep in mind, wet saws are very rare in Thailand and there aren't many choices.

Next I started pre-soaking the bricks and using mortar between them.

This refractory mortar seems very unusual to me. The mortar comes pre-mixed in a zip-tied bag placed in a 5 gallon black bucket. The instructions specifically state the mortar should be used on dry, clean bricks. Per other recommendations, I pre-soaked. I might try a test not pre-soaking to see how that acts. Another forum member, Vinz, recommended I mix in sand to make it "more like normal mortar." I tried mixing in sand, then sand and brick sand (recovered from wet saw). For me, both mixes made the mortar more difficult to use. The mortar acted like the opposite of a super-saturated solution (more dissolved matter than can be supported by liquid, slighted agitation results in a solid); if I let it stand, it acted kind of like warm butter. However, any agitation at all caused the mortar to liquify. I could place a scoop of the gelatin like mortar on a brick and immediately stand the brick on end without the mortar sliding off. However, if I combined two bricks, both with some mortar on the side, when the mortar met the whole mess liquified and fell all the way to the bottom.

Next, I tried just the mortar. I mixed it (per instructions to "re-homogenize"), placed it on bricks and it would hold. Better yet, I could use a putty knife to wedge more mortar into the joins. With the sand, I had to let it dry significantly before I could do that. At least for me, this BST AM 30 pre-mixed refractory mortar is easiest to work with by itself.


You might notice in this picture a vertical crack. Contrary to instructions on the package, I did pre-soak all the bricks. I don't know if this is serious or superficial. I wedged the ones I found. I will test the joints for strength when I return next week.


Where I could with the mortar I had prepared, I covered the exterior (about 3/4's of the way) with mortar. I will find out if that helped or hurt next week.


This brings me up through yesterday, Friday the 17th. I will return to do further work on the 25th or 26th.

[TxGR]

Labeled all the bricks (tape on top and written in Sharpie on side).


Drilled 1/2" weep holes. I expected this to be simple. I purchased the correct bits and had multiple drills. I drilled at the intersection of tiles to make starting easier. Five holes took 3-4 hours and I went through several bits. In the end, for three of the holes I had to knockout the final cm with a piece of rebar and a hammer.

My advice for others? Measure where you want them and put wooden dowels in the wet cement of the hearth.




Here is the ceramic fiber board arranged, centered, and marked.


Cut fiber board with a table saw and sabre/jig saw. No issues. As simple as the drilling should have been.

Then I started replacing the bricks, hoping everything would line up and still be centered. I was within 1cm, so I think a margin of less than 1% is acceptable here.

Final dry fitting:


With the extra fiber board, I cut what I hope will be a core for the door. I have no idea how I will encase it in something metal or durable, but if I find a way, I now have an insulated core.



More to come to catch up, but I will post tonight.

[TxGR]

Here are the revised drawings. I'll do a jpg of the first and then try to attach the pdfs in case they are useful to anyone. The brick files give the dimensions and angles for the archway bricks for even mortar lines. I did 5mm mortar lines. Now that I've used this mortar, I wish I had asked for 2mm or 3mm. I will try it this way though.



BRICK 1.pdf
BRICK 2.pdf
OVEN - REVISED.pdf

[TxGR]

Time to lay out the floor and cut bricks. I built a wooden "brick" which I could accurately place in the center of where the oven should be. Instead of using the IT, for which I had no pen attachment, I bought an inexpensive metal protractor with a centimeter scale out to 77cm. Curiously enough, the center hole of the protractor was at 70cm. I then drilled holes at the radius I wanted and used a Sharpie to mark the circle on the bricks. Many Sharpies were sacrificed in the making of this oven.


I first drew the interior dimensions of the oven, 55cm. I then drew a line for exterior cuts of the floor at 78cm (11.5cm for the brick, 1.5cm for the buffer). After lining up some bricks in a soldier configuration, I figured that was way too much buffer. I came back to 77cm.



I quickly discovered the limitations of my wet *tile* saw. The maximum depth cut of wet saw is 36mm (the brick is 75mm thick) is really not attainable because of the way the motor is mounted. My little 4" grinder helps in a few places and is easy to handle, but the depth of cut is really too shallow. The big 7" grinder is a massive, heavy beast I can't maneuver with any precision - again helpful in very limited situations. After trying the grinders, I decided the wet saw was by far the best tool available to me. I just have to make up to four cuts. Fortunately, it has a very precise laser and I can line it up on a previous cut. So, I started making cuts, which don't look elegant at all.

At some point, I started trying to use pencil to mark lines. The wet saw effectively erases chalk lines and pencil lines. Back to Sharpies. I went looking for other colors, expecting red to be good. Turned out red and green were almost useful. Pink however, turned out to be very usable.



Well, the curves will all be covered by mortar. The straight cuts look better.



I redid the inside arch form based on revised plans from my dad (thanks!!). It is now lower and less deep. The picture above shows how the inside of the bricks will be clipped to follow the oven internal radius. These are not the final bricks. I will reuse cut bricks where I can but some of these are too short. All the chalk lines are to keep center and proper orientation with the hearth.


Now I made the outer arch form. Here I am dry fitting bricks for the gateway columns before I mark and cut the approach/entry bricks. The isolated brick on the left edge is the "core brick." I've made sure it will fit in place of the wood "brick," but the fit will be tight.


Oven floor cut. Now I need to put ceramic fiber board under it.

[TxGR]

I saw this picture, but I wasn’t tracking how you made the angles. I will search for the appropriate thread and consider it.

Yes, the arch form is too wide (deep) and I plan to redo it.

thanks for feedback and suggestion.